1. Field of the Invention
The present invention relates to a near-field light generating device and a method of manufacturing the same, the device being intended for use in heat-assisted magnetic recording where a recording medium is irradiated with near-field light to lower the coercivity of the recording medium for data recording, and to a heat-assisted magnetic recording head that includes the near-field light generating device.
2. Description of the Related Art
Recently, magnetic recording devices such as a magnetic disk drive have been improved in recording density, and thin-film magnetic heads and recording media of improved performance have been demanded accordingly. Among the thin-film magnetic heads, a composite thin-film magnetic head has been used widely. The composite thin-film magnetic head has such a structure that a reproducing head including a magnetoresistive element (hereinafter, also referred to as MR element) for reading and a recording head including an induction-type electromagnetic transducer for writing are stacked on a substrate. In a magnetic disk drive, the thin-film magnetic head is mounted on a slider that flies slightly above the surface of the magnetic recording medium.
To increase the recording density of a magnetic recording device, it is effective to make the magnetic fine particles of the recording medium smaller. Making the magnetic fine particles smaller, however, causes the problem that the magnetic fine particles drop in the thermal stability of magnetization. To solve this problem, it is effective to increase the anisotropic energy of the magnetic fine particles. However, increasing the anisotropic energy of the magnetic fine particles leads to an increase in coercivity of the recording medium, and this makes it difficult to perform data recording with existing magnetic heads.
To solve the foregoing problems, there has been proposed a method so-called heat-assisted magnetic recording. This method uses a recording medium having high coercivity. When recording data, a magnetic field and heat are simultaneously applied to the area of the recording medium where to record data, so that the area rises in temperature and drops in coercivity for data recording. The area where data is recorded subsequently falls in temperature and rises in coercivity to increase the thermal stability of magnetization.
In heat-assisted magnetic recording, near-field light is typically used as a means for applying heat to the recording medium. A known method for generating near-field light is to irradiate a plasmon antenna, which is a small piece of metal, with laser light. The plasmon antenna has a near-field light generating part which is a sharp-pointed part for generating near-field light. The laser light applied to the plasmon antenna excites surface plasmons on the plasmon antenna. The surface plasmons propagate to the near-field light generating part of the plasmon antenna, and the near-field light generating part generates near-field light based on the surface plasmons. The near-field light generated by the plasmon antenna exists only within an area smaller than the diffraction limit of light. Irradiating the recording medium with this near-field light makes it possible to heat only a small area of the recording medium.
There has been known a triangular plasmon antenna such as one described in JP 2005-4901 A. JP 2007-257753 A describes a micro optical recording head that has a plasmon probe (plasmon antenna) of triangular-prism shape embedded in its core, and a method of manufacturing the same. According to this manufacturing method, a V-shaped groove is formed in a first core layer, and then a metal film is formed on the first core layer. The metal film is then removed from the areas other than the groove by polishing so that the first core layer and the metal film are flattened at the top. A second core layer is then formed over the first core layer and the metal film.
In order to increase the recording density of the magnetic recording device, the near-field light preferably has a smaller spot diameter. To generate near-field light that has a small spot diameter and sufficient intensity, it is effective to form the near-field light generating part of the plasmon antenna into a more sharply pointed shape and to concentrate more surface plasmons at such a near-field light generating part. When actually fabricating a plasmon antenna, however, there has conventionally been the problem that the near-field light generating part becomes roundish, so that it has been difficult to concentrate a lot of surface plasmons at a near-field light generating part of pointed shape.